JPH0365597A - Production of optically nonlinear crystal - Google Patents

Abstract

PURPOSE:To make possible produce KTP single crystal without blowhole within crystal and obtain optically nonlinear crystal useful for optical wave length- converting technique by setting molar ratio of raw material of KTP single crystal in a specific range and pulling up single crystal from melt. CONSTITUTION:In production of KTiOPO4(KTP) optically nonlinear single crystal by pulling up single crystal from raw material melt, molar ratio (K/Ti) of raw material composition in said melt is set in a range of 0.1-3. An oxide single crystal of K and Ti (KTiOPO4 single crystal) is able to be melted at a temperature below 1000 deg.C by flux method and crystal growing is relatively ready. Furthermore, a crystal having excellent quality without composition variation or opacifying, etc., as phase transition does not occur below melting point. Besides, generation of blowhole within crystal is inhibited by setting molar ratio (K/Ti) of raw material in a range of 0.1-3 to afford a crystal sufficiently available to practical use.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a nonlinear optical crystal, and particularly to a method for manufacturing a nonlinear optical crystal used for generating harmonics of light.

(Prior Art) Conventionally, when a certain type of crystal is irradiated with light, harmonics of the irradiated light are obtained, which is the so-called 5HG (Second I
larmonlc Generation). This type of crystal is called a nonlinear optical crystal, and for example, when a nonlinear optical crystal is irradiated with 1006 μm infrared light from a YAG laser, green light with a wavelength of 1/2 is obtained. Optical wavelength conversion technology that uses such nonlinear optical crystals to generate light that cannot be obtained with ordinary lasers is attracting attention.

Indicators of SHG performance include: ■ high conversion efficiency; ■ phase matching angle (the angle at which the phase velocity of the main wave and the phase velocity of the extremities match) is within an easy-to-use range and is wide; ■ It must be transparent and stable, etc.

What is conventionally known as SHG crystal is KDP
, L iN b O] , ]β-BaB204:
'There is. However, these crystals have advantages and disadvantages.

For example, KDP is water soluble and unstable. L i
Although high-quality crystals of NbO have been obtained, conversion efficiency is low when devices are manufactured using bulk crystals. Also,
β-BaB204 has no hygroscopicity and has a destruction threshold of 2GW.
/c12, and is transparent and exhibits excellent conversion efficiency for wavelengths of 0.19 to 2.5 μm (for example, C, Chcn
at at; Sci, Sin+ca 82g (198
5) See 235). However, β-BaB204 has a phase transition temperature close to its melting point, making it difficult to form crystals.

On the other hand, as an alternative to these crystals, KTP (KT
IOP 04) Single crystals are attracting attention. but,
Regarding this K T P i11 crystal, there are problems such as the presence of avl "s" in some places in the grown crystal, which poses practical problems as an optical element.

(Problems to be Solved by the Invention) As described above, conventionally known nonlinear optical crystals have advantages and disadvantages, and none of them are satisfactory. In particular, the KTP single crystal is the best in other respects, but
There was a problem with the presence of "su" in the crystal, and this was a factor that hindered the application of KTP single crystals to optical wavelength conversion technology.

The present invention has been made in consideration of the above-mentioned circumstances, and its purpose is to provide KTP with no "s" in the crystal.
! 1j-A nonlinear optical path that can produce crystals and is suitable for use in optical wavelength conversion technology, etc.! The object of the present invention is to provide a method for manufacturing a nonlinear optical crystal that can obtain l^.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to manufacture a nonlinear optical crystal by optimizing the molar ratio of the raw material composition of a KTP single crystal.

That is, the present invention pulls a single crystal from a raw material melt and produces K T
In the nonlinear optical crystal method for producing a P (K Ti OP 04 ) single crystal, the raw material composition molar ratio (K/Ti) in the raw material melt is in the range of 0.1 to 3, preferably 1.3 to In this method, the value is set within the range of 2.

(Function) Oxide fli viscous crystal of potassium (K) and titanium (Ti)
(K-Ti-0 single crystal) "K Ti OP 04
The illumination is melted at tooo°C by the flux method.
The crystal growth is relatively easy.

Furthermore, since there is no phase transition below the melting point, there is no compositional variation or opacity, and high quality crystals can be obtained. In addition to this, as in the present invention, the raw material composition molar ratio (K/Ti)
If it is set in the range of 0.1 to 3, the generation of "s" in the crystal can be suppressed, and the optical element can be sufficiently used in practical use.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a sectional view showing a schematic structure of a crystal pulling apparatus according to an embodiment of the present invention. In the figure, 10 is a container;
This container 10 houses a platinum crucible 11 filled with raw material melt 20. The crucible 11 is a support stand 12
A support shaft 13 perpendicular to the support stand 12 is attached to the lower surface of the support stand 12. The support shaft 13 is the container 10
It is installed through the bottom of the chamber, and can be rotated and raised by an external drive.

In addition, this support shaft 13 is provided with an Al
A thermal lightning pair 14 is attached for stabilization.

At the top of the crucible 11 is an alumina shield member 1 for heat insulation.
5 are arranged, and furthermore, alumina shield members 16 for heat insulation are arranged at the bottom and sides of the crucible 11. The crucible 1 is then closed by these shield members 15 and 16.
1 is surrounded. A heater 17 is pushed inside the shield member 16, and the crucible 11 is heated by the heater 17.

Further, above the crucible 11, a support rod (crystal pulling rod) 21 that can rotate and move up and down is installed, and a seed crystal 22 is attached to the lower end of this support rod 21. Then, by bringing this seed crystal 22 into contact with the raw material melt 20 and pulling it up, the crystal is pulled up and grown. In the figure, 25 indicates an A11l window, and 26 indicates an atmosphere adjustment port.

Next, a method for manufacturing a KTP single crystal using the apparatus configured as described above will be described.

In this example, the raw material was set to be in excess of K Ti OP O4 (the molar ratio of K H2P 04 / Ti O2 was 2), and was added to about 100 g of K
H2PO4 (potassium dihydrogen phosphate) and TiO2 (titanium dioxide) are used. Furthermore, 4P2 as a flux
A mixture of 07 (potassium pyrophosphate) and KPO3 (potassium metaphosphate) was used, and the ratio of KTP to flux K T P /Flux was set to 0.75. Each raw material 20 is housed in a platinum crucible 11 of a pulling device shown in FIG.

First, the heater 17 is heated and held at too much degree Celsius for 10 hours to completely melt and react the raw material 20 in the crucible 11 and to degas it. Next, the seed crystal 22 is added to the raw material melt 2.
0 so that the seed crystal 22 becomes compatible with the raw material melt 20. After that, slow cooling was performed at a rate of 1°C per hour.
Perform crystal growth. At this time, the crucible 11 and the seed crystal 22
are 5. Apply forpm rotation.

The pulling is performed by pulling the seed crystal 22 at a rate of 1 as/hour. Then, when the temperature reaches 800°C, growth is stopped and the grown crystals are removed from the melt.

The KTP 111 crystal thus obtained had a diameter of I cm, a length of 1, and a length of 5 cm, and microscopic observation revealed that no microscopic holes were observed inside the crystal, and it was completely transparent without any cloudiness. there were.

Next, in the above example, the raw material composition was set to the excess side, but when it was set to the excess Ti side (K/Ti molar ratio 0.5), the diameter was 1 ctn and the length was 1.5 cm. Completely transparent crystals were obtained. Furthermore, in the K-excess region, K/
When the Ti molar ratio was set to 3.5, the diameter was still 1.
A transparent crystal of cm, length l, 5e+1 was obtained.

FIG. 2 shows the transmittance using light absorption for the crystal obtained above. The solid line A represents the crystal obtained at a Ti/Ti molar ratio of 2, the dashed line B represents the crystal obtained at a Ti/Ti molar ratio of 0.5, and the dashed line C represents the crystal obtained at a Ti/Ti molar ratio of 3.5. A comparison of the obtained crystals is shown below.

From the figure, the reason why the obtained crystal is transparent to shorter wavelengths is K.
/ Ti molar ratio is 2.0.5 and 3.5 is 10
It shifted to the longer wavelength side by about 0 Å. However, even at a K/Ti molar ratio of 0.5, there was an absorption shoulder around 4000 to 5000 Å, and at a K/Ti molar ratio of 3.5, the absorption shoulder was large.

Here, when we experimented with various molar ratios, we found that when the molar ratio was less than (1.1), "su" was formed inside the obtained crystals, resulting in a noticeable white turbidity. The ratio is 3
In the above case, the absorption decreases greatly in the vicinity of 4,000 to 5,000 Å, which is the blue region, and the light extraction efficiency deteriorates significantly. Therefore, the molar ratio must be set in the range of 0.1-3. Further, when the molar ratio was in the range of 1.3 to 2, completely transparent crystals were obtained, and no decrease in absorption in the blue region was observed, resulting in improved light extraction efficiency.

Each of the crystals has a Q-switch YA with an average output lOW.
When irradiated with a G laser (wavelength to, e μm), emission of green SH with a wavelength of 5300λ was observed.

[Effects of the Invention] As detailed above, according to the present invention, by suppressing the K/Ti composition molar ratio within the range of 0.1 to 3, completely transparent monoviscous KTP without optical deterioration can be produced. crystals are obtained, especially K/
It has been found that a Ti molar ratio in the range of 1.3 to 2 is particularly good, and a nonlinear optical crystal with high conversion efficiency can be realized.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing the schematic structure of a crystal pulling apparatus used in an embodiment of the present invention, and Fig. 2 shows crystal growth by changing the K/Ti composition molar ratio using the flux method according to the present invention. FIG. 2 is a characteristic diagram comparing the light absorption of each single crystal obtained in the above. 10... Container, 11... Crucible, 17...
Heater, 20... Raw material melting, 21... Support t+,
22... Seed crystal.

Claims (1)

[Claims] A method for producing a KTiOPO_4 nonlinear optical single crystal by pulling a single crystal from a raw material melt, characterized in that the raw material composition molar ratio (K/Ti) in the raw material melt is set in the range of 0.1 to 3. A method for manufacturing nonlinear optical crystals.